1. Field of the Invention
The present invention generally relates to a method of annealing a semiconductor and a semiconductor formed by the method and more particularly, to a method of annealing a semiconductor by conducting a low temperature anneal and a high temperature anneal. More specifically, an exemplary embodiment of the invention includes a multiple step heating procedure which removes, first, physically-adsorbed water, followed by a second heating to remove chemically-adsorbed water. Another exemplary embodiment of the invention includes a semiconductor device which includes a dielectric including regions separating a plurality of metal conductors, the regions including an upper interface and a lower bulk region, the upper interface having a density greater than a density of the lower bulk region.
2. Description of the Related Art
Time dependent dielectric breakdown (TDDB) testing is commonly used to test semiconductor devices such as semiconductor wafers or chips to evaluate the susceptibility of the inter-level dielectric material (ILD) between neighboring metal lines to electrical breakdown.
During production a wafer may be partially built and a thin capping layer may be placed on the unfinished wafer (i.e., a wafer without a final passivation layer may be produced). The wafers can then sit in the fabrication environment or may be in transit for a time period prior to running a TDDB reliability test. During this period water may contaminate the unfinished wafer by being adsorbed both physically and chemically into the unfinished wafer. Water contamination into a semiconductor device has a detrimental effect on TDDB lifetimes.
The TDDB reliability testing performed on partially built wafers with water absorption produce results which are often orders of magnitude worse than the same wafers would have had without water absorption. Therefore, the TDDB reliability test results are not particularly indicative of the reliability of the partially built wafer.
In addition, if the integrity of a fully passivated chip is compromised, such as damage occurring to an edge seal during dicing, then water may enter the chip at an ingress point due to the damage. Similarly to the above scenario, water may then be adsorbed both physically and chemically into the chip. As a result of this water contamination, the result of the TDDB reliability test can be orders of magnitude worse than the same chip would have had without the water absorption. Thus, the TDDB reliability test of the chip will not be particularly indicative of the reliability of the fully passivated and fully sealed chip. Therefore, meaningful TDDB testing on water contaminated semiconductor devices cannot be conducted.
The ability to test partial-build structures for TDDB by removing any moisture effects would greatly reduce cost and turnaround time because no final passivation layers would have to be used in the build.
Despite many attempts over the years, there is currently no process which successfully removes water from the wafer or from individual chips in order to conduct a reliable TDDB test.